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          <h1 class="post-title" itemprop="name headline">单例模式</h1>
        

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        <p>单例模式是一种很常用的设计模式，很多时候，我们不需要每次都创建一个实例，全局拥有一个实例就行了，这个时候我们就需要使用设计模式了。<br>具体使用如下：<br>public class Main {<br>    /*<em>
     </em></p>
<pre><code> * SingleInstanceClass1 无锁懒汉式,单线程情况下可以使用
 * SingleInstanceClass2 有锁懒汉式,多线程情况下可以使用,效率较低
 * SingleInstanceClass3 双重锁懒汉式,多线程情况下可以使用
 * SingleInstanceClass4 饿汉式,多线程情况下可以使用,没有懒加载
 * SingleInstanceClass5 静态内部类,多线程可以使用
 */
public static void main(String[] args) {
    SingleInstanceClass1 instance1=SingleInstanceClass1.getInstance();
    SingleInstanceClass2 instance2=SingleInstanceClass2.getInstance();
    SingleInstanceClass3 instance3=SingleInstanceClass3.getInstance();
    SingleInstanceClass4 instance4=SingleInstanceClass4.getInstance();
    SingleInstanceClass5 instance5=SingleInstanceClass5.getInstance();
}
</code></pre><p>}</p>
<p>1.懒汉式(非线程安全)</p>
<p>public class SingleInstanceClass1 {<br>    private static SingleInstanceClass1 instance;</p>
<pre><code>private SingleInstanceClass1() {

}

public static SingleInstanceClass1 getInstance() {
    if (instance == null) {
        instance = new SingleInstanceClass1();

    }
    return instance;
}
</code></pre><p>}</p>
<p>2.懒汉式(同步锁，线程安全)</p>
<p>public class SingleInstanceClass2 {<br>    private static SingleInstanceClass2 instance;</p>
<pre><code>private SingleInstanceClass2() {

}

public static synchronized SingleInstanceClass2 getInstance() {
    if (instance == null) {
        instance = new SingleInstanceClass2();

    }
    return instance;
}
</code></pre><p>}</p>
<p>3.懒汉式(双重检验)</p>
<p>public class SingleInstanceClass3 {<br>    private static SingleInstanceClass3 instance;</p>
<pre><code>private SingleInstanceClass3() {

}

public static  SingleInstanceClass3 getInstance() {
    if (instance == null) {
        synchronized (SingleInstanceClass3.class){
            instance = new SingleInstanceClass3();
        }


    }
    return instance;
}
</code></pre><p>}</p>
<p>4.饿汉式</p>
<p>public class SingleInstanceClass4 {<br>    private static SingleInstanceClass4 instance=new SingleInstanceClass4();</p>
<pre><code>private SingleInstanceClass4() {

}

public static SingleInstanceClass4 getInstance() {

    return instance;
}
</code></pre><p>}</p>
<p>5.静态内部类</p>
<p>public class SingleInstanceClass5 {</p>
<pre><code>private SingleInstanceClass5() {

}

public static class SingleInstanceHolder {
    private final static SingleInstanceClass5 instance = new SingleInstanceClass5();
}

public static SingleInstanceClass5 getInstance() {

    return SingleInstanceHolder.instance;
}
</code></pre><p>}</p>

      
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